


protect you if i could

by hyliank8



Category: Undertale (Video Game)
Genre: (for once!!), Alternate Universe - Underfell (Undertale), Angst, Bite marks, Blood and Injury, Bruises, Evil Asgore, Healthy Sanster, Hurt/Comfort, Implied/Referenced Rape/Non-con, M/M, Noncon Kingdings, Power Imbalance, Powerlessness, Protective Sans (Undertale), Protectiveness, Rape Aftermath, Swearing, Underfell Asgore Dreemurr, Underfell Sans (Undertale), Underfell W. D. Gaster, W. D. Gaster is not related to Skelebros, no really there's actually Comfort this time i promise, vague description of rape/non-con
Language: English
Status: Completed
Published: 2020-11-29
Updated: 2020-11-29
Packaged: 2021-03-10 05:53:39
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,864
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27799534
Author URL: https://archiveofourown.org/users/hyliank8/pseuds/hyliank8
Summary: Gaster has a meeting with his King that... doesn't go well.Sans does his best up the pieces, but there's only so much he can do.(Underfell AU)
Relationships: Asgore Dreemurr/W. D. Gaster, W. D. Gaster/Sans
Comments: 8
Kudos: 40





	protect you if i could

**Author's Note:**

> hi!!! it's kinda been a while. life is hell rn tbh. 
> 
> this fic is sorta borderline T-rated bc nothing bad actually Happens in it, it's all just referenced. it was rated T previously but i changed it just in case, idk ;p regardless, make sure u read the tags, pls
> 
> hope u will enjoy :)

“ ‘dings? you in there?”

Sans lightly knocks on the door to Gaster’s personal quarters. He knows the scientist was particularly anxious earlier about the meeting he was set to have with the King. Gaster tried to hide it, as he always does—the stubborn monster would rather lose a limb than admit he’s not emotionless—but the extra jitter in his conjured hands’ movement as he worked this morning betrayed his true feelings. At least, to someone who knows him as well as Sans does.

Even if he’s sure Gaster won’t be honest with him, Sans still wants to check in with him to see if he wants to talk about how it went. To show he cares, or whatever. Gaster always appreciates things like that in his own abrasive way.

There’s still no answer at the door after a few moments. But where else would Gaster be? 

Sans sighs, and turns the doorknob. “i’m comin’ in.”

“Fucking christ— would it kill you to _wait_ a minute—” comes the snarl from the other side of the door. 

Sans ignores it, pushing the door open. “tooooo late, sorry. shoulda answered when i knocked.”

“Ugh, fine.” 

Entering the room, Sans sees Gaster standing in front of the full-length mirror next to his bed, shifting his gaze from his reflection to focus on Sans instead. Distantly, Gaster’s position strikes Sans as odd—the scientist is not usually one to care much about his appearance at the end of the day when there’s no longer anyone around to intimidate.

But as Sans moves further into the room and gets a closer look, he realizes Gaster isn’t in a state to be intimidating anybody anyways.

Gaster’s deep red sweater is untucked, ruffled as though it hasn’t seen an ounce of care in days, and it looks like it’s... torn, too, in some places. It’s Gaster’s favorite sweater, and it’s always kept immaculate—to the point where seeing it in anything but perfect condition sets Sans on edge, let alone the state it’s in now. Gaster’s eyes are dark and puffy around the edges in a way that Sans has seen so few times before, and Sans’ soul clenches in sympathy.

Gaster did not look like this a few hours ago.

“holy shit. uh, you look awful,” Sans deadpans.

“Thanks, Sans.” Gaster crosses his arms—but it looks like he’s hugging himself more than anything else. God, he sounds so _tired_.

“...how was the meeting with the king?”

Gaster’s eyelights flick to the side for a moment. “It was... fine. Asgore... simply wished to discuss the Core’s most recent readings. He had me give him a full report, so it took a while.”

“uh-huh.”

Gaster makes some sort of attempt at a scowl at Sans’ obvious disbelief, but it barely reaches his tired eyes. “What’s with that tone? You know, just because you _think_ you may know something, doesn’t mean that you have to—”

“you’re shaking.” Sans cuts him off, moving to approach his partner when he notices the slight tremble in his folded arms. The exposed sliver of his wrist is a few shades darker than the ivory of his natural skin tone, too. “and your wrist is bruised,” he adds.

Gaster freezes with his mouth open mid-sentence, his bright pupils shrinking to pinpricks for a split second before he snaps back into his composure. He takes a half-step back as Sans moves towards him.

“I—I don’t—you’re seeing things.”

“i know i’m not. c’mere.” Sans reaches for his partner’s arm when he nears him.

Gaster flinches away. “I’m _fine_ ,” he snarls, voice trembling. “I don’t— I don’t need— I—”

“slow down,” Sans makes a point to keep his voice calm. “wingdings... you’re safe with me. you know that. please let me see.”

Gaster watches him for a moment, a silent battle visibly taking place in his mind. But finally he gives a single, small nod.

“thank you for trusting me. here.” Sans gingerly pulls at Gaster’s wrist, bringing his partner’s arm closer to him.

“i’m going to roll up your sleeve, okay?”

Gaster gives him another slight nod, taking a deep breath as if to steel himself. Sans carefully bunches up and folds the stretchy, high-quality fabric a few times, each fold exposing more of Gaster’s arm.

And upon seeing the state of his partner’s wrist, Sans wishes he’d taken a breath to prepare himself, too.

With the shadows of his sleeve removed, it’s clear that Gaster’s wrist is bruised much worse than Sans realized. The pale skin is mottled with ugly shades of black and blue, and... is that blood dripping down his arm? He doesn’t see a wound, so the source of it must be hidden but that’s _definitely_ blood and there’s a _lot_ of it, god— 

“holy shit,” Sans breathes. “did he hurt you somewhere else too?”

Gaster opens his mouth as if to say something, then closes it again and glances off to the side, intentionally avoiding Sans’ searching gaze. So rarely has Sans seen Gaster at a loss for words.

The hand in Sans’ hold is trembling.

“...please show me, ‘dings. i see the blood. i promise i’m not going to hurt you.” Sans’ resists the urge to tighten his grip on his partner’s hand in a gesture of comfort, worried that it would hurt him. The fact that Sans has to walk on eggshells to get Gaster to cooperate, to convince him that he won’t be hurt... it makes Sans’ soul twist horribly in his rib cage. This is _Gaster_ , one of the most stubborn, powerful, prideful monsters in the Underground. He’s never seen Gaster so afraid around him, afraid _of_ him.

Anger flares deep within Sans’ soul.

Asgore did this.

There’s a special place in hell waiting for the King, and Sans will be very happy to personally escort him there later. But for now, he pushes his rage aside. Gaster needs him.

“I have to, um...” Gaster makes a vague gesture towards his sweater with his free hand.

Sans nods, easily understanding what he means. He releases Gaster’s wrist. “do you need help taking it off?”

“...Please.”

“okay. i have to touch you though, okay?”

Gaster nods, so Sans gently catches the hem of his sweater and helps him out of it. Gaster’s wince is not lost on Sans as he lifts his arms up over his head to allow the sweater to come off.

As Sans pulls the sweater off the rest of the way, he reflects that under different circumstances he would be much more enthusiastic about getting to undress Gaster like this. Still, the closeness to his partner is steeped in a gentle intimacy that brings Sans some piece of mind. Even if Gaster was hurt before, he’s safe now—he’s here, with Sans, and Sans won’t let any more harm come to him. He’ll be sure of it.

He tosses the sweater lightly onto the bed next to them, then takes a step back to give his partner a bit more room and to get a better look at the damage to his body.

Sans’ soul stutters in his chest.

The blood dripping down Gaster’s arm is from... an oddly crescent-shaped mark, a _huge_ one, on his shoulder. And that’s not the only one—there are more on his collarbones, his chest, his other arm—and _all_ of them are enormous. There’s not as much blood as Sans would expect from wounds that large—it looks like they’ve been wiped clean once already at least, but they haven’t been properly attended to. 

“shit, ‘dings—why didn’t you bandage yourself?”

Gaster shrugs noncommittally, a slight waver to the movement. 

Sans notices that more bruises litter his lover’s body, too, and while they’re not as large there’s still a _lot_ of them. Oddly, most of them mar his body in smaller clusters, some of which form scattered lines or arcs. They almost look like—

Sans’ soul turns to ice.

“gaster.... these are....”

Fingerprints.

And when Sans takes a numb step forward, he can see the small, individual punctures to his partner’s skin that make up the crescent-shaped wounds. They’re— _bite_ marks.

There’s only one pair of hands in the Underground large enough to leave bruises that size. Only one set of teeth that could leave marks like that. These aren’t wounds from a battle, or from any single attack. They’re the marks of someone who’s been held down, held in place against their will.

All of the pieces of the puzzle fall into place and a very _clear_ image of what happened sears in Sans’ mind.

“i’m going to fucking _kill that bastard_ ,” Sans snarls. “i’m going to fucking _kill_ him, there’s no _fucking way_ he’s getting away with this shit, i _swear to fucking god—_ ”

“Sans.” Gaster’s voice is quiet but firm, in stark contrast to the fact that he’s shaking, Gaster’s _shaking_ and Asgore did this, how dare _anybody_ _ever lay a hand on Gaster—_

“ _Sans._ ” Gaster makes a point to speak louder.

Sans blinks hard, Gaster’s voice forcing the hot anger to the back of his mind. Gaster needs him, he reminds himself. That’s what matters right now.

“god— sorry, ‘dings. shit.” Sans tries to think clearly as the cloud of rage in his mind thins, but he’s still at a loss for words, still trying to process what he’s seen, the jarring conclusions he’s drawn.

“It’s fine.”

Sans opens his mouth to protest that because it’s _not_ fine, but all he can do right now is work on fixing the damage that’s already been done, so he stops himself. He takes a careful breath instead.

“is it okay if i heal you?” 

Gaster hesitates, his bright pupils flickering nervously to the side again.

“please.” Sans prompts again, almost desperate. “i want to help you.”

“It’s...” Gaster still looks like he wants to protest, but he meets Sans’ gaze and whatever he sees there seems to convince him. “...okay, yes. Fine. I want to sit on the bed, though.”

“ ‘course, yeah. c’mon.”

Sans takes him gently by the hand, walking over with him to sit on the edge of his bed. Sans turns towards Gaster and raises his hands towards his chest, letting the warm green glow of his recovery magic spill forth.

They’re silent for a moment as Sans works on one of the particularly nasty bruises on his chest. The cloud of worry in Sans’ mind thins a bit when he notices the bruise start to melt back into the pristine white tone of his lover’s skin, and he’s able to think a bit more clearly again.

“Can you tell me what happened?” Sans speaks gently as he moves seamlessly onto the next bruise.

Gaster is silent for a moment, looking intently down at his hands folded nervously in his lap. “It, just.... it was just a normal meeting, at first. I was there last week, too, for a report—you know that. So I suppose it felt off from the start that he was asking for another full report so soon. But... obviously I prepared one anyway, and I gave my report just as thoroughly as I would any other. But then, he...”

His hands clench around one another in his lap, and consequently has to Sans stomp down another flare of anger that threatens to rise beyond his control.

“He interrupted me in the middle of it. He started asking about my... personal life.” Gaster tilts his head up to fix Sans with a weary look. “And then he asked about you.”

Sans’ brow furrows. “why the hell would he do that? as far as he’s concerned i’m just your assistant, right?” He thought they’d been so careful to keep their relationship a secret. The Underground has never been a place where public affection has no consequences; emotional ties to other monsters can always be exploited by adversaries and used to cause harm. To show love is to show weakness in the Underground. LOVE, on the other hand...

“It sounded like... he knew, somehow. He already knew, he just wanted to hear me... s-say it.” 

Gaster’s voice chokes up at the end of his sentence, and Sans resists the urge to abandon his healing to pull him into a hug.

Gaster is silent for a moment, gathering his voice before pressing on. “He already knew, and he threatened your well-being as a consequence for a lie. So I... I was honest. And I didn’t understand why he was asking... why he would care about that. But then he reminded me of our last meeting. You and I... had a date planned right afterwards, and I wanted everything to be perfect. It was just after the blaster incident, and you’d been worried sick about me. And I wanted to make it up to you, so I was trying to get through the report as quickly as I could so I could be on time for our date.”

Something twinges in Sans at the fact that Gaster felt the need to “make it up to him” over anything, let alone an incident that only caused _Gaster_ physical harm. No one in the Underground would believe that the great Royal Scientist would feel such a way, certainly. Sans loves being able to see Gaster’s hidden compassionate side, but... they have some things to work on with regards to his self-worth. Sans wants to protest, but he holds himself back from interrupting—Gaster is struggling to speak as it is, so Sans stays silent, focusing instead on putting all of the positive intent he can muster into his healing magic.

“I tried not to make it obvious; I was simply... efficient in my delivery. But of course he could tell, of _course_ he knew something was up. It feels as though... as though he knows what I’m thinking, sometimes, I swear. I don’t—” Gaster chokes up again, eyes squeezing shut and his expression pulling into a pained grimace. “I d-don’t even... feel safe in my own mind around him.”

Sans has never seen Gaster—elegant, cunning, powerful W. D. Gaster—so inarticulate, so unable to form words. He wants to speak up then, to reassure Gaster that he’s safe—that Asgore can’t hurt him anymore, that Asgore couldn’t possibly know everything about him. But he knows that would be a lie, so he lets Gaster continue, keeping his focus on the healing that’s nearly finished.

“He must’ve—he must’ve watched from the cameras he ordered Alphys to install in the Castle, watched us meet up afterwards. B-because I’d been acting suspicious, it was my own damn fault, a-and h-... h-he...” Gaster’s shaking returns with a vengeance, his shoulders trembling as he clenches his scarred hands around one another. Sans moves onto the last bruise with one hand, and finally rests his other hand gently over Gaster’s, wary of touching him too insistently and overwhelming him.

“He said h-he... wanted to remind me that I belong to no one but my k-... my king.”

Sans’ soul drops. Gaster is shivering worse than before—and now the anger, the pure _hatred_ towards the King in Sans’ soul is back in full force. More than ever, Sans wishes that intent alone could kill a monster from a distance. He’s sure Asgore would drop dead on the spot.

“ ‘dings, hey...” Despite his anger, Sans’ voice is filled with sympathy. He hopes Gaster isn’t forcing himself through the story for his sake.

“A-and h-he, he pushed me over the table and—” Gaster’s voice pitches an octave higher in distress. “A-and he... was so _rough_ and it hurt so badly and I f-f-felt like I couldn’t even br-breathe, the aura of his magic was s-suffocating, and it was so _humiliating_ and I didn’t want it, I wanted him to stop but I c-c-couldn’t— I _couldn’t_ fight him and I didn’t want him to hurt you and _I’m sorry I wasn’t stronger, I’m s-so s-sorry, Sans—_ ”

“ ‘dings— shit, slow down, okay?” The last bruise finally disappears, and Sans brings his other hand down into Gaster’s lap to hold both of his trembling ones. Gaster clings to him like a lifeline, as though Sans is the only thing grounding him. “can i touch you, please? more than this?”

Gaster jerks his head down in a shaky nod.

Sans immediately pulls him into a protective embrace, wrapping his arms around his lover’s bare shoulders and holding him close. It’s a little difficult to envelop Gaster completely in his hold given Sans’ relatively small size, but Gaster leans into his touch regardless.

“listen. this wasn’t your fault, okay?” Sans is adamant. “asgore’s the worst piece of shit in the underground and he _deserves_ to burn in hell. you have nothing to be sorry for, you hear me? nothing.”

“But I j-just— I j-just _let_ him,” Gaster says quietly, his voice still a broken rasp. “I let him do what he wanted with me, I didn’t p-put up a fight—”

“you didn’t have a choice,” Sans says. “you _didn’t_ have a choice, ‘dings, you _cannot_ blame yourself for this. please.”

Gaster is silent for a moment, leaning into Sans’ hold, but his trembling doesn’t falter.

“I f-feel... so disgusting...” he whispers. “It h-hurt more than _anything_ ever has, and I th-thought he was going to k-kill me... and I’ve never been so _afraid_ before, not in my entire life.“

“but you’re here now,” Sans murmurs. “i’m right here with you. and i’ll fucking kill him, i’ll send him to hell myself, you hear me?”

“St- _stop_ ,” Gaster says, just as distressed. “Stop _saying_ that, Sans. You know you’d never be able to take him, and I can’t stand the thought of you being hurt.”

“oh, yeah? _i_ couldn’t take him?” Sans challenges.

“I-I... I checked his L-LOVE. He’s at Level 17. Even with you being unnaturally powerful for your size, he could cr-crush you like a bug w-without batting an eye.”

“holy shit.” 

Seventeen is a lot higher than the last time Sans remembers hearing about the King’s Level of Violence. He heard that there were some attempted uprisings in New Home, and those always end in monsters being killed—but he didn’t realize there was _that_ much carnage.

“H-he could crush— a- _any_ of us... he was so p-powerful, and I had no choice but to take it and I’ve never felt so _powerless_ and—”

“hey, hey—c’mon, remember to breathe,” Sans cuts him off before his sentence can devolve into hysteria once more. He begins running a soothing hand up and down his lover’s back, hoping to ground him with the soft touch. “i’m here now. we’ll figure this out together.”

Sans wills himself to believe his own words in the hopes that that will somehow coax Gaster into believing them too. 

But... how? How could they _ever_ figure this out? Asgore is the King; anything he says goes. If he wanted to hurt Gaster every day for the rest of his life, he could. If he wanted to kill Sans, he could do that, too. It would be easy for him; even if he didn’t have immensely powerful magic, he still has nearly the entire Monster Kingdom at his command. 

Sans has no real power here to help Gaster, and from the way his lover meets his eyes for a moment before quickly shifting his gaze back down to his hands, it’s clear Gaster is well aware of that fact, too. 

Gaster manages to calm his trembling after a few long moments, his normally-sharp eyes dulling with grim acceptance. His gaze fixes aimlessly on some spot on the floorboards beneath them.

Sans can see it in expression. Gaster knows it just as well as he does. If Asgore wants to hurt his Royal Scientist again, he will—and Sans will be able to do nothing to stop it.

Stars, Sans doesn’t want to think about that.

“...do you have anything else that you need me to heal?” Sans’ question is, admittedly, partially an effort to distract them both from the bleak conclusion they’ve mutually drawn. Still, he can’t imagine the skin covered by Gaster’s slacks suffered no injury from the King’s wrath.

“No, no, I can... I can manage those just fine.” Gaster squeezes Sans’ hands gently one last time before letting go and moving to stand, eyes still noticably fixed on the floor. “I’m going to go get washed up.”

Sans’ brow furrows. “are you sure?”

Gaster nods, decidedly not raising his gaze to meet his lover’s eyes. “I don’t want you to... see me like that,” he says quietly.

“i...” Sans immediately feels the urge to protest—he’d never judge Gaster for weakness, never in a million years, and the fact that Gaster suddenly feels the need to hide himself even from his lover makes his magic boil in his soul (how _dare_ the King hurt him like this, _how dare he_ ). But he holds back his objection—Gaster’s pride is everything to him, and letting Sans heal him as much as he did has surely already taken a toll on him. So Sans shuts his mouth, justifying to himself that he’ll ask again later if he needs to; perhaps if Gaster ends up really struggling, Sans can wear him down a bit more into letting himself be healed again.

“okay. i understand. i’ll wait here for you, okay?”

“Okay. And, Sans...” Gaster glances tenuously back up at him. “...if I slept here tonight, would you stay with me?”

Sans gives him a soft smile. “yeah, sure thing, ‘dings. i’ll let paps know. think he was gonna spend the night at ‘dyne’s anyways.”

A little bit of life comes back into Gaster’s eyes at that. Sans can’t help the delicate hope that buds in his soul at that, and he stands and closes the half-pace between them.

“one more thing before you go.”

Sans places a gentle hand on the nape of Gaster’s neck to guide him down into a sweet kiss. Sans’ magic sparks where Gaster’s lips meet his mandible, and the reciprocating spark from Gaster’s soul says more than either of them could ever communicate with words.

Sans breaks from the kiss reluctantly, but he stays in place with his forehead pressing against Gaster’s for a long moment.

“Thank you for healing me,” Gaster murmurs.

“you don’t have to thank me. i’ll always heal you.” He says it without a shred of hesitation in his mind. It’s one of the few constants in his dangerous, fickle life; he’s _always_ there for Gaster. Gaster’s _always_ there for him. Nothing will ever change that.

Unwillingly, Gaster finally pulls away, and Sans watches him make his careful exit for the washroom connected to his personal quarters. Once his lover has disappeared from his view he retreats to the bed once more, this time pulling himself all the way onto it. 

As Sans allows himself to collapse fully onto his back, he makes a distinct effort to pretend he didn’t notice Gaster’s limp as he walked away. It doesn’t work much. 

Sans’ eyelights fix sightlessly onto the blank ceiling above as he awaits Gaster’s return, feeling more powerless than he ever has.

**Author's Note:**

> anddd asgore sees that both of them entered the lab and neither of them exited at the end of the night bc he’s a creep, so. things get worse from there. but who knows when i’ll finish writing that loooool
> 
> ironic that the longest healthy sanster fic i've written so far is underfell, huh.
> 
> if u wanna come say hi on [tumblr](https://hyliantimelordin221b.tumblr.com/) or [twitter(18+ only)](https://twitter.com/K8Maybe) feel free 2 do so!! :)
> 
> i was doin my best to post at least one fic a month which has worked for the past 10-ish months but life is a bit rough rn so idk if it will be that frequent going forward, at least for a bit :( i dunno for sure tho!! thank u to all of u who leave such sweet comments, reading them makes me sososo happy ;~;
> 
> thank u for reading!!!!! if u comment i lov u


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